Electrical conductivity studies on LAMOX based electrolyte materials for solid oxide fuel cells

Abstract

In this study, the electrical conductivity of the LAMOX based electrolytes (La<inf>1.8</inf>Dy<inf>0.2</inf>Mo<inf>2-x</inf>W<inf>x</inf>O<inf>9</inf> (x = 0, 0.1, 0.2, 0.5, and 1), and La<inf>1.8</inf>Dy<inf>0.2</inf>Mo<inf>2-x</inf>Ga<inf>x</inf>O<inf>9</inf> (x = 0.1)) synthesized by the citrate complexion method has been studied using DC four-probe method. The electrical conductivity of the electrolytes is measured in the temperature range of 800–400 °C in the air (∼100 ml min−1). The effect of W and Ga substitution at the Mo site on the electrical conductivity is evaluated. The long-term electrical conductivity stability test (time on stream) (5 h) is conducted at 650, 580, and 520 °C to study the effect of possible phase transition on electrical conductivity. A high-temperature XRD study is also conducted in the temperature range of 500–650 °C (during heating and cooling) on selected electrolyte materials (La<inf>1.8</inf>Dy<inf>0.2</inf>Mo<inf>2-x</inf>W<inf>x</inf>O<inf>9</inf> (x = 0 and 0.1) and La<inf>1.8</inf>Dy<inf>0.2</inf>Mo<inf>2-x</inf>Ga<inf>x</inf>O<inf>9</inf> (x = 0.1)) to study the α↔β phase transition. The electrical conductivity of these electrolytes in the air at 800 °C is in the range of 5.3 × 10−2 – 14 × 10−2 S cm−1. The activation energy (E<inf>A</inf>) of these electrolytes is in the range of 1.11–1.62 eV. The VTF parameters σ<inf>o</inf>, B, and T<inf>o</inf> are in the range of 67.46–395.88 S cm−1 K0.5, 0.122–0.254 eV, and 247–347 °C, respectively. The La<inf>1.8</inf>Dy<inf>0.2</inf>Mo<inf>2-x</inf>W<inf>x</inf>O<inf>9</inf> (x = 0.1) shows highest electrical conductivity (14 × 10−2 S cm−1, E<inf>A</inf> = 1.54 eV) among all electrolytes in air at 800 °C and for this material the VTF parameters σ<inf>o</inf>, B, and T<inf>o</inf> are 170.32 S cm−1 K0.5, 0.153 eV, and 302 °C, respectively. © 2022 Elsevier Ltd and Techna Group S.r.l.